Tum yum soup is a chinese soup with a nice thai twist to it. Lemon grass and lemon are added in good measure to give this soup a nice, summery flavor. It is a clear soup and makes an ideal appetizer if you have a heavy main course that follows. Lemon grass and vinegar add in more tartness and vegetables like mushroom and cauliflower comprise the bulk of the soup. You can experiment with vegetables, and try it with carrots, french beans and baby corn too. It is a very soothing and fragrant soup that tastes delicious.